State Key Laboratory of Integrated Management of Pest Insects and Rodents in Agriculture, Institute of Zoology, Chinese Academy of Sciences, China.
University of Chinese Academy of Sciences, Beijing, China.
Integr Zool. 2022 Mar;17(2):206-216. doi: 10.1111/1749-4877.12543. Epub 2021 Jun 4.
Beyond direct species interactions, seed dispersal is potentially affected by indirect seed-seed interactions among co-occurring nut-bearing trees which are mediated by scatter-hoarding animals as shared seed dispersers. A relevant question in such systems is to what extent different functional traits related to food palatability and profitability affect the kinds of indirect interactions that occur among co-occurring seeds, and the consequences for seed dispersal. We used field experiments to track seed dispersal with individually tagged seeds in both monospecific and mixed seed communities. We measured indirect effects based on 3 seed-seed species pairs from the family Fagaceae with contrasting seed size, tannin level, and dormancy in a subtropical forest in Southwest China. When all else was equal, the presence of adjacently placed seeds with contrasting seed traits created different indirect effects measured through a variety of dispersal-related indicators. Apparent mutualism was reciprocal due to increasing seed dispersal in mixed seed patches with mixed differences in seed tannins and dormancy. However, differences in either seed size or dormancy in co-occurring adjacently placed seeds caused apparent competition with reduced seed removal or seed dispersal (distance) in at least one species. Our study supports the hypothesis that different functional traits related to food palatability and profitability in co-occurring seeds modify foraging decisions of scatter-hoarding animals, and subsequently cause indirect effects on seed dispersal among rodent-dispersed trees. We conclude that such indirect effects mediated by shared seed dispersers may act as an important determinant of seed dispersal for co-fruiting animal-dispersed trees in many natural forests.
除了直接的物种相互作用外，种子传播还可能受到散生贮藏动物作为共享种子传播者介导的共生坚果树种之间间接种子-种子相互作用的影响。在这种系统中，一个相关的问题是，与食物适口性和盈利性相关的不同功能特征在多大程度上影响共生种子之间发生的间接相互作用，以及对种子传播的影响。我们使用野外实验，在单种和混合种子群落中使用单独标记的种子来跟踪种子传播。我们通过来自壳斗科的 3 个种子-种子种对测量间接效应，这些种对具有不同的种子大小、单宁水平和休眠性，研究地点位于中国西南地区的一个亚热带森林中。在其他条件相同的情况下，具有不同种子特征的相邻种子的存在会产生不同的间接效应，这些效应可以通过各种与传播相关的指标来衡量。由于混合种子斑块中混合的单宁和休眠差异导致种子传播增加，明显的互利互惠是互惠的。然而，在共生的相邻种子中，种子大小或休眠的差异会导致在至少一个物种中出现明显的竞争，从而减少种子的去除或传播（距离）。我们的研究支持了这样的假设，即与共生种子的食物适口性和盈利性相关的不同功能特征会改变散生贮藏动物的觅食决策，从而对啮齿动物传播的树木之间的种子传播产生间接影响。我们得出的结论是，这种由共享种子传播者介导的间接效应可能是许多自然森林中动物传播的果实共享树木种子传播的一个重要决定因素。
